Add color hints to text blocks, use explicit <br> instead of whitespace

[C0rn3j]

Fixes up the coloring of code blocks.

Unifies some of the code blocks (there was a file with triple backticks for the first command, but used single backtick format for the rest).

Fixes a syntax error in objects.md where it used quadruple backticks once.

Converts whitespace line breaks to explicit <br> tags, as whitespace can be inconsistent and people can randomly litter it on accident - which is exactly the case of some of the touched up files.

Note that the shell commands remain mostly uncolored, but I tagged them anyway, as some editors do support the tags, even if GitHub doesn't.

Is adding a changelog fragment necessary for just a doc change?

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[C0rn3j]

CLA signed.

[bobapple]

@cla-bot check

[mkayontour]

Hi sorry, for the late reply. I can add the changelog later on, the changelog will created automatically based on the fragments. So it's easier to keep track over the changes and also highlight contributors in the release notes. ;)

This looks good to me.

[Donien]

Thank you very much for your work and getting rid off these pesky little trailing whitespaces!

Just apply the suggestions. Other than that we're good. Thanks :)

[C0rn3j]

@Donien Thanks for the review, I've applied all the suggestions